I just converted my 1 HP portable dust collector to a two stage unit with a 'regulation' size bag.
The good news is that it seems to suck fairly well, almost as good as running with no bag. Whereas the suction with the mini bag was pathetic. The bad news is that the hose whistles like a banshee now with the table saw reducer attached (2.25"). I'm not sure if it's whistling through the opening or around the connection, but I suspect the opening.
Any thoughts on reducing this noise? It's intolerable, even with the ears on.